Hydromechanical properties of subgrade soil and effects of quicklime-stabilization: case of Kombe–Mbanga road in Cameroon

This study characterizes the geotechnical properties and stabilization potential of lateritic soils along the Kombe-Mbanga road corridor, focusing on their hydromechanical behavior and interaction with existing pavement structures. This study provides a comprehensive geotechnical characterization of subgrade soils along the Kombe-Mbanga road, addressing a critical gap in Cameroon’s infrastructure design standards. Additionally, it conducts a statistical analysis of lime stabilisation. Given the high clay content in general and active mineral composition, these soils exhibit significant swelling-shrinkage cycles, posing challenges for long-term road performance. The primary objective is to determine the optimum quicklime dosage required to stabilize the soil and mitigate deformation risks effectively. A series of laboratory tests were conducted on natural and lime-stabilized soil samples using 2%, 4%, and 6% quicklime by weight of dry material. The analyses included physical soil identifications, hydromechanical analysis at the laboratory, and statistical factor analysis to interpret stabilization efficiency. The natural soils contain 39–62% fines, they are plastic soil (IP: 10.66–29.86%) with a moderately to highly compressible coefficient (Cc: 0.10–0.41) and low swelling potential (Cs: 0.01–0.05), primarily classified as Illite dominant content. Stabilization results indicate that 2% quicklime provides the most effective balance, significantly reducing Cc and Cs while maintaining optimal soil structure and strength. Statistical analyses (Pearson correlation and PCA) confirmed strong negative relationships between lime content and both Cc (-0.36) and Cs (-0.53), within Factor 1 explaining 58.4% of variance in stabilization effectiveness. While most soils responded best to 2% lime.